A dual clutch is arranged for coupling an engine-side output shaft to two different transmission input shafts arranged coaxially in relation to each other. A dual clutch has a first clutch and a second clutch, wherein both the first clutch and second clutch have a pressure plate that is axially movable relative to a counter-plate for engaging the clutch with an associated transmission input shaft. In addition, a co-rotating clutch cover is bolted to a second counter-plate which is then bolted to the first counter-plate. Also, an actuation means is axially fixed for moving the first pressure plate and/or the second pressure plate.
Dual clutch transmissions in motor vehicles increase overall performance by reducing the alternating time between gears within a transmission when compared to a single clutch system and increase engine efficiency by being able to more accurately select the appropriate gear within a transmission. Traditional single and double clutch systems use the same axial arrangement between the flywheel and clutch discs. In current dual clutches, the clutch discs are circular plates axially arranged with a flywheel, which is also a circular plate, and must have a greater force of friction between the clutch discs and flywheel than that of a force imparted by the rotational momentum of the flywheel. Conical surfaces can be used as the contact area between the flywheel and clutch discs to take advantage of the rotational forces developed within a clutch assembly. This is disclosed in U.S. Pat. No. 2,247,478 (Burtnett) where a flat, traditional clutch disc engages the flywheel and then a conical shaped clutch engages the first clutch in order to spin both transmission input shafts. Due to the first clutch and second clutch being in close proximity to one another, the heat generation within the clutch assembly could reach a critical level and cause failure of the device. In addition, power transfer to the conical clutch is transmitted from the flat clutch disc, which is still susceptible to slipping due to its means of engagement with the flywheel.
Another version of a conical clutch is described in U.S. Pat. No. 2,126,760 (Eason) where a single clutch system is described. This patented invention includes a single conical clutch within the assembly that is driven by the flywheel and engages a conical surface axially arranged on an output shaft. The conical clutch disc is of spoked construction to allow for airflow through the clutch disk to prevent overheating. This spoked design arguably improves cooling of the clutch disk, but it limits the performance of the clutch disk due to a decrease in structural strength and prevents the assembly from being used in high load situations where cooling of the assembly would be a major concern.
Clutch discs are designed from low density, high strength material and contain the least amount of material possible to reduce their rotational inertia. A major downside of this design is that with a lighter clutch disc, there is less material to absorb and dissipate the heat generated by the engaging and disengaging of the clutch discs with the flywheel. This generation of heat can be detrimental to the operating efficiency of the dual clutch and lead to mechanical failure due to expansion and fatigue of major components including the flywheel, pressure plates, and clutch discs. To increase the safety factor of the major components, these parts are cast from cast iron, high strength steel, or aluminum due to these materials' superior heat dissipation properties and high strength. Cast iron, which is a less expensive and popular casting material for flywheels, is dense and heavy which increases the chance of slip between the clutch discs and flywheel due to the high rotational inertia generated.
Thus, there has been a long-felt need for a dual clutch, and, even more particularly, for a dual clutch having two conical discs engaged on opposite sides of a single flywheel for alternating gears in a transmission. There has also been a long-felt need for a flywheel having a base and a frusto-conical member emanating from and extending upwardly from the base.